The Jewish community in Corinth, from which some of them came (Acts 18:1–8), would have referred to themselves as the church of God.
But Paul reminds the Corinthian Christians that they are the true church of God.
In both Jewish and pagan circles, holiness was closely associated with temple service. Yet Paul tells his readers that they are the ones who have been sanctified
(set apart or made holy) and called to be saints.
Although they have no part in any earthly temple service, they are in Christ Jesus.
They take part in Christ’s worship in the heavenly temple.
Paul also reminds the Corinthians that they share their calling with all the followers of Christ everywhere. In the Old Testament, those who serve the God of Israel are often described as those who call upon the name of the Lord.
Paul picks up on this expression but clarifies it. The Lord
is none other than our Lord Jesus Christ.
2 To the church of God that is in Corinth, to those sanctified in Christ Jesus, called to be saints together with all those who in every place call upon the name of our Lord Jesus Christ, both their Lord and ours: